Effect of Hemostatic Agents on Shear Bond Strength of Orthodontic Eyelets Bonded with Conventional and Self-etch Adhesives

Statement of the Problem: The risk of debonding of the orthodontic eyelets due to blood contamination from the impacted tooth is a clinical problem that orthodontists face routinely. Purpose: This study aimed to assess the effect of hemostatic agents (Viscostat clear and Astringedent X) on shear bond strength (SBS) of orthodontic eyelets bonded with conventional (Transbond XT) and universal adhesive (GC-G Premio bond) adhesives. Materials and Method: In this experimental study, 84 freshly extracted bovine lower incisors were randomly divided into 7 groups namely TBXT, Blood, SEP, VISCO + TBXT, VISCO + SEP, ASTX + TBXT, and ASTX + SEP groups. In the TBXT group, teeth were etched with phosphoric acid gel, and then, the Transbond XT primer was applied and eyelets were bonded with Transbond XT. In the blood group, first, contamination with blood was done followed by the same procedure as TBXT. In other groups, the teeth were etched with phosphoric acid and based on their group allocation, Transbond XT primer (in TBXT groups), GC-G Premio Bond (in SEP groups), ViscoStat Clear gel (in VISCO groups), or Astringedent X (in ASTX groups) were applied. The SBS was measured for each group and the adhesive remnant index (ARI) was determined. Results: The mean SBS was 20.79 MPa in VISCO+SEP group, 19.2 MPa in the TBXT group, 16.06 MPa in the SEP group, 15.43 MPa in VISCO+TBXT group, 9.39 MPa in AST-X+TBXT group, and 1.62 MPa in the blood group. The SBS of ASTX+SEP, blood and TBXT+ASTX groups had significant differences from the SBS of the control group (p< 0.05). The ARI score of 0 had the highest frequency in the blood group. Conclusion: Due to the high coagulative effect of Astringedent X and acceptable SBS of Astringedent X in combination with GC-G Premio bond, this combination can be recommended for exposure of impacted teeth that are at high risk of blood contamination.


Introduction
An impacted tooth is a permanent tooth whose more than three-quarters of the root is formed and its selferuption in a reasonable time is unexpected. Two differ-ent methods are applied in the clinics for the exposure of impacted teeth including close surgical exposure and open surgical exposure [1]. For bonding an attachment to the impacted teeth in the field of surgery and achieve-ng a clinically acceptable SBS of attachments, maintaining appropriate hemostasis during bonding is crucial.
Enamel bonding, which is the key procedure in either restorative or esthetic treatments, has been always challenging [2]. Conventionally, etch and rinse adhesives are used as the most popular adhesion approach in dentistry, but today, they are somehow substituted by self-etch adhesives for their more convenient handling and efficiency in bonding to enamel [3]. However, the new self-etching approaches have some disadvantages too. For example, the acids with higher pH used in such adhesives provide less enamel demineralization and weaker enamel bonds compared to phosphoric acid that is used in conventional etch and rinse approaches [4].
The bond-strengthening effect of the acid etching method is following the hydroxyapatite dissolution that creates regular microporosities, which increase the surface area for adhesion [5]. In self-etch adhesives, on the other hand, the acidic functional monomers interact with the mineral component of enamel providing the etching function [3]. In addition, the inter-prismatic acid etching pattern is deep in conventional adhesion approaches, while this pattern in self-etching techniques is absent to moderate. However, the enamel bond strength in these systems stays acceptable, regardless of their minimal acid attack on enamel [4,6]. Accordingly, Brackett et al. [7] claim no essential correlation between the bond strength and deep inter-prismatic acid attack. Whereas, Dalton et al. [8] addressed lower bond strength to enamel for self-etching systems compared to the conventional systems. Therefore, the efficacy of using phosphoric acid before self-etching approaches has been suggested to increase the retentive strength of selfetching adhesives [4].
In the new adhesion approaches, self-etching primers with less application time and no need for a completely dry surface, namely wet bonding, are used for bonding attachments [9].
Nowadays, contamination with blood and detachment of orthodontic attachment from impacted tooth surface is a clinical problem that results in more treatment duration, additional charges for the patient, and difficulties for both clinician and patient. Hemostasis is a complicated process with three major phases including vasoconstriction, platelet plug formation, and coagulation (in secondary hemostasis). Hemostatic agents in-crease hemostasis capacity either mechanically or by stimulating the coagulation cascade [10]. Chemical hemostatic agents are categorized as Class I (vasoconstrictors, adrenergic) and Class II (hemostatic agents, Astringedents) groups. Astringedents such as aluminum chloride, Alum (aluminum potassium sulfate), and zinc chloride sediment proteins on the surface of the mucosa and its mechanical strengthening. Stypics such as ferric sulfate and ferric chloride are concentrated forms of Astringedent and result in surface and local coagulation [11]. Astringedent X (Ultradent Products Inc., South Jordan, Utah, USA) is composed of 12.5% iron with an equal presence of ferric sulfate and ferric subsulfate.
Hemostatic agents with more acidity are more effective in coagulation but they are harmful to tissues [12].

Study design and experimental groups
According to Oksayan et al. [13] and using one-way analysis of variance (ANOVA), the least sample size was 12 samples in each group. This experimental study was conducted in vitro using 84 freshly extracted bovine lower incisors. At first, all tissue that remained around the root surface of teeth was mechanically removed, and then, teeth were washed under running tap water. For later usages, they were stored in distilled water. Then, teeth were randomly divided into seven groups (n=12) including TBXT group, blood group, SEP group, VISCO + TBXT group, VISCO + SEP group, ASTX + TBXT group, and ASTX + SEP group. Before removing, all tooth surfaces were cleaned with toothpaste, fluoride-free pumice, and water for 10 seconds. After every 5 times, the prophylaxis of the rubber cap was changed to ensure its proper functioning. The teeth were then fixed on a wax plate and then, the buccal surface of the teeth was examined for any enamel failure by the light-pass method using a stereomicroscope (Konix-120, Germany) at a magnification of 10X. Any enamel cracks and structural failures were confirmed. In the TBXT group, teeth were etched with phosphoric acid gel for 20 seconds and rinsed for 20 seconds, then, Transbond XT primer was applied and light-cured for 10 seconds. In the blood group, teeth surfaces were etched for 20 seconds and rinsed for 20 seconds. Then, they were contaminated with fresh blood of the author immediately after donating using a syringe and needle and the Transbond XT primer was applied and light-cured for 10 seconds. In this group, no type of anticoagulant was used and contamination with the blood sample was immediately performed after obtaining it. In the SEP group, teeth were etched with phosphoric acid for 20 seconds, and then, GC-G Premio bond (Japan, GC Corporation) was applied on the surface and lightcured for 10 seconds. In the VISCO + TBXT group, teeth were etched with phosphoric acid for 20 seconds, then, ViscoStat Clear (Ultradent, South Jordan, Utah, ABD) was applied for 2 minutes using a special syringe and tip, then, rinsed for 30 seconds. After, the Transbond XT primer was applied and light-cured for 10 seconds. In the VISCO + SEP group, teeth were etched with phosphoric acid for 20 seconds, then, Vis-coStat Clear was applied for 2 minutes using a special syringe and tip and rinsed for 30 seconds. Then, the GC-G Premio bonds were applied and light-cured for 10 seconds. In the ASTX + TBXT group, teeth were etched with phosphoric acid for 20 seconds, and then, Astringedent X (Ultradent, South Jordan, Utah, ABD) was applied for 2 minutes using a special syringe and tip and rinsed for 30 seconds. After, the Transbond XT primer was applied and light-cured for 10 seconds. In the ASTX + SEP group, teeth were etched with phosphoric acid for 20 seconds, then, Astringedent X was applied for 2 minutes using a special syringe and tip, rinsed for 30 seconds, and GC-G Premio bond was applied and cured with light for 10 seconds. In all groups, the eyelets (Henry Schein Orthodontics, Melville, N.Y, USA) were bonded on the middle of the crowns with Transbond XT adhesive. After mounting, the teeth were thermocycling and SBS was measured by a universal testing machine. The adhesive remnant index (ARI) was also measured.

SBS
After bonding, all specimens were stored in distilled water at 37±1ºC for 48 hours. Before testing, they were also thermal-cycled 3000 times between 5 ºC and 55 ºC.
Samples were jigged using acrylic blocks. A stainless steel wire (0.2 mm diameter) was used to connect the samples to the jig. A 1mm/min force was applied on the samples until fracture happened and the maximum- The surface area of eyelets was 14.14mm 2 , according to the factory information. Bond strength was measured with a shear test, and failure modes were assessed.
For evaluating the ARI, the buccal surface of each tooth was observed by a stereomicroscope (Konix-120, Germany) with 10× magnification and scored according to Artun and Bergland criteria [14].

Statistical analysis
The obtained data were analyzed by one-way analysis of variance (ANOVA) using SPSS software version 22.0 (SPSS, Inc., Chicago, IL, USA). For showing the main effect of treatments, means were compared by Tukey-Kramer test. Kruskal-Wallis test was used for the analysis of ARI data. A p< 0.05 was considered statistically significant.

Results
The shear bond strengths of orthodontic eyelets bonded using the conventional and self-etch adhesives are represented in Table 1 showed a statistically significant difference with ASTX groups was not statistically significant ( Figure 1).
Based on Table 3, the blood group showed the most prevalence for zero grade of ARI index and ARI Index score 1 was the most prevalent score between different groups.     In terms of mechanism, the self-etching dental adhesion systems effectively bond to the enamel surfaces through the nano-retentive interlocking between crystallites and the thin hybridized complex of adhesive resin formed in the enamel, despite the lower bond strengths presented by some self-etching systems [17]. In this regard, the acidic resin monomers within the self-etch adhesives eliminate the need for a prior etching step on dental substrates by phosphoric acid. It is noteworthy that the resin monomer composition, water content, and acidity of different self-etch adhesives are variable [31].
On the other hand, in routine orthodontic procedures, a safe debonding of brackets is more important than maximum bond strength [32]. According to factory Astringedent X is a stronger hemostat agent than Viscostat clear .Moreover, it is reported that self-etch primers like Gc-G Premio bond combine two crucial steps of the bonding process and perform better than total-etch systems in wet fields, on the other hand, the SBS of this combination is within the acceptable clinical range [28].
Due to the high coagulative effect of Astringedent X and acceptable SBS of Astringedent X and GC-G Premio bond combination, they can be recommended for exp-osure of impacted teeth at high blood contamination risk.
Considering the reliability of ARI scores for determ- Epinephrine, and Astringedent that we could not use in our groups because of the limitation of study samples.

Conclusion
Using Viscostat clear in addition to GC-G Premio bond had probably the highest SBS, and this combination is recommended for exposure of impacted teeth in normal condition. Due to the high coagulative effect of Astringedent X and acceptable SBS of Astringedent X and Gc-G Premio bond combination, they can be recommended for exposure of impacted teeth at high blood contamination risk and they can be used for patients at high risk of bleeding, including hemophilic patients.